Producing method of film with through-holes

ABSTRACT

A film is made of an elastic material. The film is stretched in at least one direction in parallel to a surface of the film. Then, through-holes are punched in the film be means of needles, in a state the film is stretched. After the punching is completed, the stretching is terminated, so that the film recovers its original shape.

[0001] This application is a divisional of U.S. patent application Ser.No. 09/161,306, filed Sep. 28, 1998, the contents of which are expresslyincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

[0002] This invention relates to a producing method of a film withthrough-holes.

[0003] Generally, such film is made of a plastic film. A punchingmachine is used to form through-holes on the film. The punching machineis arranged to pierce the film with needles. In order to improve theaccuracy of dimensions (such as diameters and pitches) of thethrough-holes, it is necessary to improve an operation accuracy of apunching machine. However, such improvement of the punching machine mayincrease the producing cost of the film.

[0004] Accordingly, there is a strong demand for a producing method of afilm with through-holes which achieves a high accuracy of the dimensionsof the through-holes, without increasing the producing cost of the film.

[0005] Further, it is difficult to produce a film with through-holeswhich inclination angles (from a direction of a thickness of the film)are relatively large. This is because, when the film is pierced with aneedle in an inclined direction, the film tends to be bent.

[0006] Accordingly, there is a strong demand for a producing method of afilm with through-holes which inclination angles (from a direction of athickness of the film) are relatively large.

SUMMARY OF THE INVENTION

[0007] It is therefore an object of the present invention to provide aproducing method of a film with through-holes, which achieve a highaccuracy of dimensions of the through-holes without increasing theproducing cost of the film.

[0008] Further, it is another object of the present invention to make itpossible to produce a producing method of a film with through-holeswhich inclination angles (from a direction of a thickness of the film)are relatively large.

[0009] According to an aspect of the present invention, there isprovided a method including the steps of (1) stretching the film in atleast one direction in parallel to a surface of the film, (2) formingthrough-holes in the film in a state the film is stretched, and (3)terminating the stretching of the film after the through-holes areformed.

[0010] After the stretching is terminated, dimensions of the film in thestretching direction decrease. Thus, error of dimensions (such asdiameters and pitches) of the through-holes of the film also decrease.As a result, the accuracy of the dimensions of the through-holes isimproved, without improving an operation accuracy (of a punching machineor the like) in the through-hole-forming step. Consequently, it ispossible to achieve a high accuracy of the dimensions of thethrough-holes of the film, without increasing the producing cost of thefilm.

[0011] In the through-hole-forming step, it is preferred to form thethrough-holes by punching. With this, the producing cost is relativelylow (compared with a laser machining or the like).

[0012] In a particular arrangement, a clamp mechanism is used in thestretching step. The clamp mechanism holds at least two sides of thefilm to stretch the film. With this, the film can be continuouslystretched by means of a simple mechanism. Also, with such a clampmechanism, biaxial stretching is enabled.

[0013] Further, the through-holes are formed on at least one row in thethrough-hole-forming step. With this, the produced film can be employedin an ink transfer printer described below. In such case, thethrough-holes are faced with heating elements of a thermal line head.

[0014] According to another aspect of the present invention, there isprovided a producing method of a film (made of shape memory resin) withthrough-holes. The producing method includes the steps of (1) heatingthe film to a temperature above a glass transition temperature of theshape memory resin, (2) stretching the heated film in at least onedirection, (3) cooling the stretched film to a temperature below theglass transition temperature, (4) forming through-holes in the film, and(5) heating the film to a temperature above the glass transitiontemperature.

[0015] As the stretched film is cooled before the film recovers itsoriginal (non-stretched) shape, the film is solidized in a state thefilm is stretched. Thus, it is possible to keep the stretched state ofthe film without continuously applying force to the film.

[0016] In a particular arrangement, a pair of heat rollers are used toheat the film and to stretch the film. The film is inserted in a gapbetween the rollers and pressed therein, so that the film is stretched.Optionally, a fan is used to cool the film in the cooling step. The fanis located in the vicinity of the heat rollers.

[0017] According to still another aspect of the present invention, thereis provided a producing method of a film with through-holes. The film ismade of shape memory resin. The producing method includes the steps of(1) forming through-holes in the film, (2) heating the film to atemperature above a shape-providing temperature of the shape memoryresin, and (3) stretching the film in at least one direction in parallelto a surface of the film, in a state the film is heated to a temperatureabove the shape-providing temperature.

[0018] The produced film is thinner than the film in thethrough-hole-forming step. Further, dimensions of the ‘produced’ film inthe stretching direction are larger than those of the film in thethrough-hole-forming step. Thus, the inclination angles of thethrough-holes (from a direction of a thickness of the film) of theproduced film are larger than those of the through-holes formed in thethrough-hole-forming step. Accordingly, it is possible to produce a filmwith through-holes which inclination angles (from a direction of athickness of the film) are relatively large.

[0019] In a particular arrangement, a pair of rollers are used in thestretching step. The film is inserted in a gap between the rollers andpressed therein. The rollers are heated to a temperature above theshape-providing temperature.

[0020] The film produced by the above-described producing method can beused in an ink transfer printer. The ink transfer printer includes (1) athermal head comprising a plurality of heating elements, the thermalhead being faced with the film so that the heating elements are facedwith the through-holes of the film, (2) a space formed between thethermal head and the film, which holds ink therein, (3) a platen memberwhich urges a recording media to a surface of the film. When the heatingelements selectively heat the ink in the space and the film, inkpermeates the through-holes of the film and transferred to the recordingmedia.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIGS. 1A, 1B, 1C and 1D are schematic views showing a producingmethod of a film with through-holes according to a first embodiment;

[0022]FIG. 2 is a perspective view of the film of FIG. 1;

[0023]FIG. 3 is a sectional view of a ink transfer printer using thefilm of FIG. 2;

[0024]FIG. 4 is an exploded perspective view showing a main part of theink transfer printer of FIG. 3;

[0025]FIGS. 5A and 5B are schematic views illustrating ink transferringprocess;

[0026]FIG. 6 is an enlarged view of the film nipped by a thermal headand a platen roller of the ink transfer printer of FIG. 3;

[0027]FIG. 7 is a diagram showing an example of a characteristic of ashape memory resin according to the second embodiment;

[0028]FIGS. 8A, 8B, 8C and 8D are schematic views showing a producingmethod of a film with through-holes according to the second embodiment;and

[0029]FIGS. 9A, 9B, 9C and 9D are schematic views showing a producingmethod of a film with through-holes according to the third embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0030] The embodiments of the producing method of a film withthrough-holes according to the present invention are described below.

[0031]FIGS. 1A, 1B, 1C and 1D are schematic views showing a producingmethod of a film with through-holes according to a first embodiment. Afilm 2 shown in FIG. 1A is made of polytetrafluoroethylene (Teflon(trademark)). The film 2 has a square shape, each side thereof havingthe length L. The thickness t of the film 2 is from 0.03 to 0.08 mm. InFIG. 1A, X-direction and Y-direction are defined along two adjacentsides of the film 2.

[0032] As shown in FIG. 1B, the film 2 is stretched in two directions. Aclamp mechanism is used to stretch the film 2. The clamp mechanism hasfour clamps 110 which respectively hold four sides of the film 2 (one ofclamps 110 is not shown in FIG. 1B) and stretches the film 2 inX-direction and Y-direction. The film 2 is stretched so that the lengthof each side becomes 2L, and so that the thickness of the film 2 becomest/4.

[0033] As shown in FIG. 1C, through-holes 25 are punched in the film 2by means of needles 115 of a punching machine. The through-holes 25 havea certain diameter D, and are arranged on two rows with a certain pitchP. The film 2 is pierced with the needle 115 in a direction that isinclined from a direction of a thickness of film 2 to Y-direction. Thatis, the through-holes 25 are inclined to Y-direction. Due to theoperation accuracy of the punching machine, error in dimensions (such asdiameters and pitches) of the through-holes 25 is approximately 0.02 mm.After the through-holes 25 are formed, the stretching of the film 2 isterminated, so that the film 2 recovers its original (non-stretched)thickness as shown in FIG. 1D. With this, the film 2 with through-holes25 is produced. The ‘produced’ film 2 is shown in FIG. 2.

[0034] As shown in FIG. 1D, since the film 2 recovers its original(non-stretched) thickness, the thickness of the film 2 changes from t/4to t. Also, the length of each side of the film 2 changes from 2L to L.Accordingly, the diameter of the through-holes 25 changes from D to D/2.Also, the pitch of the through-holes 2 changes from P to P/2.

[0035] As a result, even if the error of the dimensions of thethrough-holes 25 is 0.02 mm in the punching step (FIG. 1C), the error ofthe dimensions of the through-holes 25 of the ‘produced’ film 2 (FIG.1D) is 0.01 mm. That is, the accuracy of the dimensions of thethrough-holes 25 is doubled.

[0036] As described above, by punching the through-holes 25 in the film2 in a state the film 2 is stretched, the accuracy of dimensions ofthrough-holes 25 can be consequently improved, without improving theoperation accuracy of the punching machine.

[0037] In the above-described first embodiment, it is possible to formthrough-holes 25 throughout the surface of the film 2. Further, it ispossible to stretch the film 2 in only one direction (instead of twodirection). In case the film 2 is stretched in Y direction, the shape ofthe through-holes 25 of the produced film 2 is ellipse that is elongatedin X direction.

[0038] An ink transfer printer using the film 2 is described. FIG. 3 isa sectional view of the ink transfer printer. The ink transfer printerincludes a thermal line head 3 having multiple of heating elements 35arranged in a row. The above-described film 2 with through-holes (notshown in FIG. 3) is supported by a board 3 a of the thermal line head 3via a spacer 8 provided therebetween, so that the film 2 and the thermalline head 3 are faced with each other.

[0039] The spacer 8 and the board 3 a of the thermal line head 3 aremade of materials which do not allow the permeation of ink. Thus, ink isstored in a space surrounded by the spacer 8, the board 3 a of thethermal line head 3 and the film 2. A platen roller 4 is provided at theopposing side of the film 2 with respect to the thermal line head 3, sothat a recording media R is sandwiched by the platen roller 4 and thefilm 2. The circumferential surface of the platen roller 4 is made ofrubber. The rotation shaft 4 a of the platen roller 4 is orientated in adirection in which the heating elements 35 of the thermal line head 3are arranged. When the platen roller 4 is rotated, the recording media Ris fed in the direction shown by an arrow in FIG. 3, due to a tractionbetween the recording media R and platen roller 4.

[0040]FIG. 4 is an exploded perspective view of the ink transfer printerexcept the platen roller 4. The spacer 8 is a thin plate member whichsurrounds the heating elements 35 of the thermal line head 3. That is,the spacer 8 defines four side borders of the ink space 1 in which theheating elements 35 are located. In order to supply ink to the ink space1, an ink tank 6 is provided on the board 3 a of the thermal line head 3so that the ink tank 6 is adjacent to the spacer 8. The ink tank 6 has anot-shown cavity in which ink can be stored. Ink stored in the ink tank6 is introduced into the ink space 1 through a slit-shaped outletopening 62 formed on the ink tank 6 and a slit-shaped connecting opening85 formed on the spacer 8, due to a capillary action. The film 2 isattached to the upper surface of the spacer 8 so that the through-holes25 are faced with the heating elements 35 of the thermal line head 3.

[0041]FIGS. 5A and 5B are schematic views showing an ink transferringprocess. As shown in FIG. 5A, the diameter of the through-holes 25 aresmall so that ink does not permeate the through-holes 25. The film 2 isalmost in contact with the heating element 35 of the thermal line head3. When the heating element 35 is heated, ink located in the vicinity ofthe heating element 35 is heated. As shown in FIG. 5B, the heated ink isvaporized and expanded, causing an increase in the local pressure ofink. Also, a portion of the film 2 located in the vicinity of theheating element 35 is heated. The elastic coefficient of the heatedportion of the film 2 decreases, so that the heated portion of the film2 is easily deformed. Due to the increase in the local pressure in ink,ink is pushed into the through-hole 25 of the film 2. Further, thethrough-hole 25 is widen so as to allow the permeation of ink. Withthis, ink permeates the through-hole 25 and is transferred onto therecording media R (FIG. 3) which is in contact with the upper surface ofthe film 2. After the heating of the heating elements 35 is stopped, theheated ink is cooled by the surrounding ink, so that the increase in thelocal pressure in ink disappears. Further, the heated portion of thefilm is also cooled by ink. With this, the widened through-holes 25recover their original diameters so that the through-holes 25 do notallow the permeation of ink.

[0042] As constructed above, by controlling the thermal line head 3 toselectively heat the heating elements 35 and by rotating the platenroller 4 to feed the recording media R, a desired image is formed on therecording media R.

[0043] In the above-described ink transfer printer, it is possible toarrange that the film 2 is sandwiched by the heating elements 35 and theplaten roller 4 as shown in FIG. 6. Since the through-holes 25 of thefilm 2 is inclined from a direction of the thickness of the film 2, thethrough-holes 25 are almost closed. With such an arrangement, even if anunintentional pressure is applied to ink (or to the film 2), anunintentional permeation of ink is prevented. Thus, the ink leakage isprevented. Further, it is possible to constitute the spacer 8 of anadhesive agent instead of the thin plate member.

[0044] The second embodiment of the present invention is described. Inthe second embodiment, a film 200 is made of shape memory resin whichexhibits different characteristics above/below a glass transitiontemperature Tg. FIG. 7 is a diagram showing an example of thecharacteristics of the shape memory resin. When the shape memory resinis heated to a temperature above a glass transition temperature Tg (andbelow a shape-providing temperature To described below) as shown by “b”in FIG. 7, the shape memory resin exhibits a rubber state, in whichBrownian motion of molecules is activated. When the shape memory resinis cooled to a temperature below the glass transition temperature Tg asshown by “a” in FIG. 7, the shape memory resin exhibits a solid state inwhich Brownian motion of molecules is frozen. Further, if the shapememory resin is heated to a temperature above ashape-providing-temperature T0 as shown by “c” in FIG. 7, the shapememory resin exhibits a fluidized state in which molecules arefluidized. In this fluidized state, the shape memory resin is given anoriginal shape. Examples of the shape memory resin are as follows: (1)polynorbornene, (2) trans-1,4-polyisoprene, and (3) polyurethane. Inthis embodiment, polyurethane resin (which is low cost and has excellentmoldability) is used. In this embodiment, the glass transitiontemperature Tg of the shape memory resin is from 60_C to 80_C. The shapememory resin is disclosed in Japanese Laid-Open Patent Application Nos.HEI 5-305666 and HEI 8-49960, teaching of which are incorporated byreference in their entireties.

[0045]FIGS. 8A, 8B, 8C and 8D are schematic views showing the producingmethod according to the second embodiment. As shown in FIG. 8A, the film200 made of the shape memory resin has a thickness t of 2 mm. This film200 is inserted in a gap between two heat rollers 210. The heat rollers210 are heated at 70_C, which is higher than the glass transitiontemperature Tg of the shape memory resin. The film 200 is heated so thatthe film 200 exhibits a rubber states and pressed by the heat rollers210, so that the film 200 is stretched in one direction (referred to asY-direction). The film 200 is stretched so that the thickness of thefilm 200 is 0.05 mm (t/40). A pair of fans 220 are located at downstreamside of the heat rollers 210. The film 200 which moves out of the gapbetween the heat rollers 210 is rapidly cooled by fans 220 to atemperature below the glass transition temperature Tg. That is, the film200 is cooled just after the film 200 is stretched and before the film200 becomes thicker. With this, the film 200 exhibits the solid state ina state the film 200 is stretched.

[0046] Further, as shown in FIG. 8C, through-holes 205 are punched inthe film 200 by means of needles 215. The diameters of the through-holes205 are denoted by D in FIG. 8C. After punching of the through-holes205, the film 200 is heated to a temperature above a glass transitiontemperature Tg by means of a heater (denoted by H′ in FIG. 8D). As aresult, the film 200 recovers its original thickness as shown in FIG.8D. That is, the thickness of the film 200 is changed from 0.05 mm(t/40) to 2 mm (t). The diameter of the through-holes 205 in thestretching direction (Y-direction) becomes D/40. With this, the film 200with through-holes 205 is produced.ü@The film 200 produced by theprocess shown in FIGS. 8A through 8D can be used as a film 2 in the inktransfer printer shown in FIG. 3.

[0047] As described above, even if the error in the dimensions (inY-direction) of the through-holes 205 is 0.02 mm in the punching step(FIG. 8C), the error in the dimensions (in Y-direction) of thethrough-holes of the produced film 200 is 0.0005 mm. That is, theaccuracy of the through-holes of the produced film 200 in Y direction isimproved. Further, since the film is solidized in a state the film isstretched, it is possible to keep the stretched state of the filmwithout continuously applying force to the film.

[0048] The third embodiment of the present invention is described. Inthe third embodiment, a film 300 is made of a shape memory resin similarto the second embodiment.

[0049]FIGS. 9A, 9B, 9C and 9D are schematic views showing the producingprocess according to the third embodiment. As shown in FIG. 9A, a film300 made of the shape memory resin has a thickness t of 2 mm. First, asshown in FIG. 9B, through-holes 305 are punched in the film 300 by meansof needle 315. The piercing direction of the needle 315 is inclined toone direction (referred to as Y-direction). The inclination angle of thepiercing direction of the needle 315 from a direction of the thicknessof the film 300 is denoted by (. The diameter of the through-holes 305is denoted by D in FIG. 8C.

[0050] After the through-holes 305 are formed, the film 300 is insertedin a gap between two heat rollers 310 in Y-direction. The heat rollers310 are heated at 150_C, which is higher than the shape-providingtemperature T0 of the shape memory resin of the film 300. The film 300is heated so that the film 300 exhibits a rubber states and pressed bythe heat rollers 310, so that the film 300 is stretched in Y-direction.The film 300 is stretched so that the thickness of the film 300 is 0.05mm (t/40). Since the film 300 is heated to a temperature above theshape-providing temperature T0, this shape of the film 300 (having thethickness of 0.05 mm) becomes an original shape of the film 300. Withthis, the film 300 with through-holes 305 is produced. The film 300produced by the process shown in FIGS. 9A through 9D can be used as thefilm 2 in the ink transfer printer shown in FIG. 3.

[0051] As shown in FIG. 9D, the inclination angle (of the through-holes305 of the ‘produced’ film 300 from a direction of the thickness of thefilm 300 is larger than inclination angle (the piercing direction (FIG.9B) of the needle 315. Accordingly, it is possible to form the film 300with through-hole 305 which inclination angle from a direction of thethickness of the film 300 is relatively large.

[0052] Although the producing method of a film with through-holes isdescribed herein with respect to the preferred embodiments, manymodifications and changes can be made without departing from the spiritand scope of the invention.

[0053] The present disclosure relates to subject matters contained inJapanese Patent Application No. HEI 09-282633, filed on Sep. 30, 1997,which is expressly incorporated herein by reference in their entirety.

What is claimed is:
 1. A producing method of a film with through-holes,said film being made of an elastic material, said method comprising thesteps of: stretching said film in at least one direction in parallel toa surface of said film; forming through-holes in said film in a statesaid film is stretched; and terminating said stretching of said filmafter said through-holes are formed.
 2. The producing method accordingto claim 1 , wherein said through-holes are formed by punching in saidthrough-hole-forming step.
 3. The producing method according to claim 1, wherein said through-holes are inclined from a direction of athickness of said film to a direction of said extension.
 4. Theproducing method according to claim 1 , wherein a clamp mechanism isused in said stretching step, and wherein said clamp mechanism holds atleast two opposing sides of said film to stretch said film.
 5. Theproducing method according to claim 1 , wherein said through-holes areformed on at least one row in said through-hole-forming step.
 6. Theproducing method according to claim 1 , wherein biaxial stretching isperformed in said stretching step.
 7. A film with through-holes producedby the producing method according to claim 1 .
 8. An ink transferprinter using said film with through-holes according to claim 7 , saidink transfer printer comprising: a thermal head comprising a pluralityof heating elements, said thermal head being faced with said film sothat said heating elements are faced with said through-holes of saidfilm; a space formed between said thermal head and said film, in whichink can be stored; and a platen member which urges a recording media toa surface of said film; wherein said heating elements selectively heatsaid ink in said space and said film, so that ink permeates saidthrough-holes of said film and transferred to said recording media.
 9. Aproducing method of a film with through-holes, said film being made ofshape memory resin, said method comprising the steps of: heating saidfilm to a temperature above a glass transition temperature of said shapememory resin; stretching said heated film in at least one direction;cooling said stretched film to a temperature below said glass transitiontemperature; and forming through-holes in said film.
 10. The producingmethod according to claim 9 , further comprising the step of heatingsaid film to a temperature above said glass transition temperature ofsaid shape memory resin, after said through-hole forming step.
 11. Theproducing method according to claim 9 , wherein a pair of heat rollersare used to heat said film and to stretch said film, and wherein saidfilm is inserted in a gap between said rollers and pressed therein, sothat said film is stretched.
 12. The producing method according to claim11 , wherein at least one fan is used to cool said film, said fan beinglocated in the vicinity of said heat rollers.
 13. A film withthrough-holes produced by the producing method according to claim 9 .14. An ink transfer printer using said film with through-holes accordingto claim 13 , said ink transfer printer comprising: a thermal headcomprising a plurality of heating elements, said thermal head beingfaced with said film so that said heating elements are faced with saidthrough-holes of said film; a space formed between said thermal head andsaid film, in which ink can be stored; and a platen member which urges arecording media to a surface of said film; wherein said heating elementsselectively heat said ink in said space and said film, so that inkpermeates said through-holes of said film and transferred to saidrecording media.
 15. A producing method of a film with through-holes,said film being made of shape memory resin, said method comprising thesteps of: forming through-holes in said film; heating said film to atemperature above a shape-providing temperature of said shape memoryresin; and stretching said film in at least one direction in parallel toa surface of said film, in a state said film is heated to a temperatureabove said shape-providing temperature.
 16. The producing methodaccording to claim 15 , wherein a pair of rollers are used in saidstretching step, wherein said film is inserted in a gap between saidrollers and pressed therein.
 17. The producing method according to claim16 , wherein said rollers are heated to a temperature above saidshape-providing temperature.
 18. The producing method according to claim15 , wherein said through-holes are inclined from a direction of athickness of said film to a direction of said extension.
 19. Theproducing method according to claim 15 , wherein said through-holes areformed on a row in said through-hole-forming step.
 20. The producingmethod according to claim 15 , wherein said through-holes are formed bypunching in said through-hole-forming step.
 21. A film produced by theproducing method according to claim 15 .
 22. An ink transfer printerusing said film with through-holes according to claim 21 , said inktransfer printer comprising: a thermal head comprising a plurality ofheating elements, said thermal head being faced with said film so thatsaid heating elements are faced with said through-holes of said film; aspace formed between said thermal head and said film, in which ink canbe stored; a platen member which urges a recording media to a surface ofsaid film; wherein said heating elements selectively heat said ink insaid space and said film so that ink permeates said through-holes ofsaid film and transferred to said recording media.